The present invention relates to a cutting tool assembly and to a self-retainable cutting insert therefor to be used in particular in internal turning operations.
When performing internal turning operations a tool holder with a cutting insert mounted therein is often used. The tool holder comprises an elongated rod with a cutting insert fastened at its front end by means of a retaining screw. When a machined bore is of a small diameter, for example, in the range of 6 mm or less, the cutting insert and the retaining screw become diminutive which results in difficult handling and poor human engineering. Moreover, the presence of a screw bore in the cutting insert limits the miniaturization of the cutting tool assembly.
A possible solution to the above mentioned problem is to produce the cutting insert and the elongated rod as an integral piece made from cemented carbide. However, such a solution is costly and does not solve the problem of the use of replaceable cutting inserts.
In U.S. Pat. No. 5,836,724 to Satran et al. there is disclosed a replaceable shim (11) for use in pockets (3) of a metal cutting tool (1). Each pocket is defined by a pair of side walls (4, 5) and a base wall (6). An elongated cylindrical recess (7), having a diameter d1, is formed at the junction of the side wall (5) and the base wall (6) and opens into the pocket (3) via an elongated slot (8). The shim (11) is formed by pressing and sintering a metal powder. The shim has an elongated rib (16) formed integrally with a substantially rectangular plate-like body portion (12). The rib is formed with strip portions (19, 20, 21) that lie on a right circular cylindrical envelope of diameter d2. In order to insert the rib (16) into the recess (7), the shim (11) is oriented with respect to the base wall (6) of the pocket (3) by an acute angle xcex1. Then, the rib (16) can be inserted into the recess (7) seeing that its minimum lateral spacing (D2) is not greater than the lateral dimension (D1) of the slot. Now, when the shim is pivotally displaced with respect to the recess (7) towards the base wall (6) of the pocket (3), the strip portions (19, 20, 21) slide in tight, frictional contact with the inner surface of the cylindrical recess (7) until the base surface (14) of the body portion (12) abuts the base wall (6). At this position, the rib (16) is tightly retained within the recess (7) and the shim, as a whole, is retained in the pocket (3).
The cutting tool of ""724 is designed to retain a replaceable cutting insert (26) on top of the shim (11). The shim serves as a support to the cutting insert, and, therefore, it is not required to dismantle the shim very often. The fact that the strip portions of the rib slide in tight frictional contact with the inner surface of the recess means that a large number of insertions of a shim within the recess will eventually cause an excessive wear of the pocket thus preventing its further use. Consequently, the cutting tool of ""724 is not provided with a resiliently displaceable clamping jaw that enable a quick and easy replacement of a cutting insert without accumulating wear to the insert pocket.
It is the object of the present invention to provide a cutting tool and a replaceable cutting insert therefor that is not affixed by a retaining screw and which can be used, inter alia, for small diameter internal turning operations.
In accordance with the present invention there is provided a cutting tool assembly (10) comprising a cutting insert holder (12) and a cutting insert (14), the cutting insert holder comprising a body portion (16) and an insert retaining portion (18) the insert retaining portion having a generally cylindrical inner surface (32) of diameter D1 and a longitudinal axis A;
the insert retaining portion (18) comprising a fixed portion (22) connected to the body portion (16) and an axially extending clamping jaw (24) having a radially facing clamping surface (42), the axially extending clamping jaw (24) being connected to the fixed portion (22) on one side along an axially extending juncture (25) and separated from the fixed portion (22) on an other side along an axially extending free end (30) by an axially extending aperture (27), the axially extending aperture (27) being bound by the free end (30) of the clamping jaw (24) on one side and by an axially extending first locating surface (36) of the fixed portion (22), adjacent the inner surface (32), on an opposite side;
the cutting insert (14) comprising a generally cylindrical portion (44) having a longitudinal axis B and an axially extending radial projection (46) connected thereto, the radial projection having upper and lower surfaces (55, 62) connected to the cylindrical portion (44) and being separated by a side surface (57), the upper surface (55) and the side surface (57) meeting at an edge, at least a portion of which constitutes a cutting edge (56), and the lower surface (62) constitutes a first locating surface; and
the cutting insert (14) being located in the insert retaining portion (18) with the axially extending radial projection (46) protruding from the axially extending aperture (27) and the first locating surface (62) of the cutting insert abutting the first locating surface (36) of the insert retaining portion (18),
characterized in that the clamping jaw (24) being separated from the body portion (16) by a slot (26), being resiliently displaceable relative to the fixed portion (22) and the cutting insert (14) being clamped in position by means of a resilient radial force exerted by the clamping surface (42) of the clamping jaw (24) on the generally cylindrical portion (44) of the cutting insert (14).
In accordance with a preferred embodiment, the cutting insert (14) is provided with an axially extending centrally located through bore (66) and the cutting insert holder (12) is provided with an associated centrally located bore (43) opening out into a back wall (45) of the insert retaining portion (18).
Preferably, the cylindrical portion (44) is of an axial extent greater than the axial extent of the radial projection (46).
In accordance with a preferred embodiment of the present invention, the generally cylindrical portion (44) of the cutting insert (14) is provided with three axially extending ribs (50, 52, 54).
Typically, two of the three axially extending ribs (50, 52) have radially outermost regions that lie on a cylindrical envelope of diameter D2 having as axis the longitudinal axis B.
Typically, D2 is equal to D1.
Further typically, one of the three axially extending ribs (54) has a radially outermost region that lies on a cylindrical envelope of diameter D3.
Preferably, D3 is greater than D1.
Further preferably, D3 is greater than D2.
In accordance with a preferred embodiment of the present invention, the three axially extending ribs (50, 52, 54) are angularly disposed by 120xc2x0 one from another, with respect to the axis B.
Typically, the cutting insert is clamped in position with the clamping surface (42) of the clamping jaw (24) abutting the axially extending rib (54) of the generally cylindrical portion (44).
In accordance with a preferred embodiment of the present invention, the clamping jaw (24) is wider at the juncture (25) than at the free end (30) and tapers from the juncture to the free end.
Further in accordance with a preferred embodiment of the present invention, the clamping jaw (24) is thicker at the juncture (25) than at the free end (30).
Yet further in accordance with a preferred embodiment of the present invention, the axially extending first locating surface (62) of the cutting insert (14) and the axially extending first locating surface (36) of the fixed portion (22) of the insert retaining portion (18) are planar.
Still yet further in accordance with a preferred embodiment of the present invention, the insert retaining portion (18) of the cutting insert holder (12) is further provided with a generally axially directed second locating surface (38) adjacent the first locating surface (36) and transverse thereto, the cutting insert (14) is provided with a second locating surface (64) adjacent the first locating surface (62) and transverse thereto, and wherein the second locating surface (64) of the cutting insert (14) abuts the second locating surface (38) of the cutting insert holder (12).
In accordance with one specific application of the present invention, the axially extending first locating surface of the cutting insert is in the form of a generally V-shaped protrusion (143) and the axially extending first locating surface of the fixed portion of the insert retaining portion is in the form of a complementary shaped V-shaped groove (135).
In accordance with another specific application of the present invention, the axially extending first locating surface (343) of the cutting insert is convex and the axially extending first locating surface of the fixed portion of the insert retaining portion is a complementary shaped concave surface (335).
In accordance with another specific application of the present invention, the axially extending first locating surface (243) of the cutting insert is concave and the axially extending first locating surface of the fixed portion of the insert retaining portion is a complementary shaped convex surface (235).
In accordance with a preferred embodiment of the present invention, the clamping jaw (24) is further provided with an axially extending groove (40) merging with the clamping surface (42) of the clamping jaw.
In accordance with another embodiment of the present invention, the cutting insert is generally symmetrical about a symmetry plane (M) and has two sets of cutting edges (456xe2x80x2, 456xe2x80x3) on both sides of the symmetry plane.
In accordance with the present invention, there is provided a cutting insert (14) for use with the cutting tool assembly (10) according to the present invention, the generally cylindrical portion is provided with three axially extending ribs, two of the three axially extending ribs (50, 52) have radially outermost regions that lie on a cylindrical envelope of diameter D2 having as axis the longitudinal axis B.
characterized in that at least a portion of the edge constitutes a cutting edge (56), one of the three axially extending ribs (54) has a radially outermost region that lies on a cylindrical envelope of diameter D3 and wherein the diameter D3 is greater than the diameter D2.
In accordance with a preferred embodiment, the cutting insert (14) is provided with an axially extending centrally located through bore (66).
In accordance with a preferred embodiment of the present invention, the three axially extending ribs (50, 52, 54) are angularly disposed by 120xc2x0 one from another, with respect to the axis B.
Further in accordance with a preferred embodiment of the present invention, the first locating surface (62) is planar.
Still further in accordance with the present invention, the radial projection (46) is provided with a second locating surface (64) adjacent the first locating surface (62) and transverse thereto.
In accordance with one specific application of the present invention, the axially extending first locating surface of the cutting insert is in the form of a generally V-shaped protrusion (143).
In accordance with another specific application of the present invention, the axially extending first locating surface (343) of the cutting insert is convex.
In accordance with another specific application of the present invention, the axially extending first locating surface (243) of the cutting insert is concave.
In accordance with the present invention, there is yet further provided an insert key (70, 500) for use with the cutting tool assembly according to the present invention, for mounting the cutting insert (14) on the cutting insert holder (12), the insert key comprising:
a peripheral surface (71) extending from a rear portion (73) of the insert key to a front portion (75) thereof and comprising a side surface (72) and a front surface (74);
a cavity (76) having a generally cylindrical inner side wall (80), the cavity opening to the front surface (74) into a substantially circular aperture (77) and opening into the side surface (72) into a substantially rectangular aperture (78) extending axially along the cavity (76) from the front surface (74) where the circular and rectangular apertures join.
In accordance with one embodiment, the insert key (70) is further provided with an elongated pin (92) concentric with the cylindrical inner side wall (80) and extending from the rear portion (73) of the insert key towards the front surface (74).
If desired, the insert key (500) is provided with an open ended sleeve (510) made from resilient material and slidably insertable into the cavity (76), the sleeve (510) having a generally cylindrical cavity (512) and a substantially rectangular aperture (513) extending along the sleeve and coinciding with the rectangular aperture (78) in the side surface of the insert key when the sleeve is located in the cavity (76).
In accordance with the present invention, there is still yet further provided an insert key (70a) for use with a cutting tool assembly according to the present invention, for removing the cutting insert (14) from the cutting insert holder (12), the insert key comprising:
a peripheral surface (71) extending from a rear portion (73) of the insert key to a front portion (75) thereof and comprising a side surface (72) and a front surface (74);
a cavity (76) having a generally cylindrical inner side wall (80), the cavity opening to the front surface (74) into a substantially circular aperture (77) and opening into the side surface (72) into a substantially rectangular aperture (78) extending axially along the cavity (76) from the front surface (74) where the circular and rectangular apertures join;
a first transverse aperture (79a) located rearward of the front surface, the transverse aperture opening from the inner side wall into the side surface and extending on the side surface transversely from the substantially rectangular aperture.
If desired, the insert key (70a) is provided with a second transverse aperture (81a) opposite the first transverse aperture with respect to the rectangular aperture (78).
In accordance with one embodiment, the insert key (70a) is further provided with an elongated pin (92) concentric with the cylindrical inner side wall (80) and extending from the rear portion (73) of the insert key towards the front surface (74).
There is also provided in accordance with the present invention, an insert key (600) for use with a cutting tool assembly according to the present invention, for mounting the cutting insert (14) on the cutting insert holder (12),
the insert key (600) comprising a base plate (602) having a plurality of insert retaining pockets (604), each insert retaining pocket comprising a peripheral surface (606) and an axial abutment surface (608) connected thereto, two retaining members (616, 618) shearingly connected to the base plate (602) detachingly retaining the generally cylindrical portion (44) of the cutting insert (14) and a cutting insert rotation prevention stopper (614) connected to the base plate (602).
In accordance with a preferred embodiment, the cutting insert rotation prevention stopper (614) is a tangentially directed portion of a radially outwardly extending groove (612) in the base plate (602).
Further in accordance with a preferred embodiment, the insert retaining pocket (604) is provided with two apertures (615, 617) located between the axial abutment surface (608) and the peripheral surface (606), a retaining member (616, 618) is located above each aperture (615, 617), the size and shape of each aperture being such as to allow the free passage of the retaining members therethrough in an axial direction.
Preferably, the retaining members (616, 618) are shearingly connected to the axial abutment surface (608) by a rim (610).
In accordance with the present invention, the slot (26) having a periphery (29) and an inner portion (31) and wherein the slot being slanted rearwardly from its periphery towards its inner portion.
In accordance with the present invention there is provided a cutting tool assembly (10) comprising a cutting insert holder (12) and a cutting insert (14), the cutting insert holder comprising a body portion (16) and an insert retaining portion (18) the insert retaining portion having a generally cylindrical inner surface (32) of diameter D1 and a longitudinal axis A;
the insert retaining portion (18) comprising a fixed portion (22) connected to the body portion (16) and an axially extending clamping jaw (24) having a radially facing clamping surface (42), the axially extending clamping jaw (24) being connected to the fixed portion (22) on one side along an axially extending juncture (25) and separated from the fixed portion (22) on an other side along an axially extending free end (30) by an axially extending aperture (27), the axially extending aperture (27) being bound by the free end (30) of the clamping jaw (24) on one side and by an axially extending first locating surface (36) of the fixed portion (22), adjacent the inner surface (32), on an opposite side;
the cutting insert (14) comprising a generally cylindrical portion (44) having a longitudinal axis B and an axially extending radial projection (46) connected thereto, the radial projection having upper and lower surfaces (55, 62) connected to the cylindrical portion (44) and being separated by a side surface (57), the upper surface (55) and the side surface (57) meeting at an edge, at least a portion of which constitutes a cutting edge (56), and the lower surface (62) constitutes a first locating surface; and
the cutting insert (14) being located in the insert retaining portion (18) with the axially extending radial projection (46) protruding from the axially extending aperture (27) and the first locating surface (62) of the cutting insert abutting the first locating surface (36) of the insert retaining portion (18),
characterized in that the clamping jaw (24) being separated from the body portion (16) by a slot (26), being resiliently displaceable relative to the fixed portion (22) and the cutting insert (14) being clamped in position by means of a resilient radial force exerted by the clamping surface (42) of the clamping jaw (24) on the generally cylindrical portion (44) of the cutting insert (14), and
wherein in a first clamping position the clamping surface (42) of the clamping jaw (24) lies on a cylindrical envelope having a second diameter (D2), wherein in a second clamping position the clamping surface (42) of the clamping jaw (24) lies on a cylindrical envelope having a third diameter (D3) and wherein the third diameter being larger than the second diameter.